This application claims benefit of priority to Japanese Application number JP 2001-236746 filed Aug. 3, 2001, the entire content of which is incorporated by reference herein.
1. Field of the Invention
The present invention relates to a speed governor that detects excessive traveling speed of an elevator cage or counterweight and to an elevator employing this speed governor.
2. Description of the Related Art
Article 129 No. 9(7) of Regulations made under regulation of the Japanese Building Standards Law specifies that, as a safety device in an elevator, there must be provided a device to automatically restrain descent of the cage if the speed of the descending cage exceeds a prescribed value.
FIG. 1 is a view showing diagrammatically the mechanism of a typical elevator provided with an emergency stop device. Elevator cage 101 is raised and lowered within an ascent/descent path (shaft) by means of a winding machine (hoist)(not shown) from which it is suspended by a main rope 102, its ascent/descent being guided by a guide rail 103 provided in the ascent/descent path. An emergency stop device 104 is mounted on cage 101. If the speed of elevator cage 101 exceeds the rated speed due to breakage of main rope 102 or abnormal increase of the speed of rotation of the winding machine, emergency stop device 104 mechanically stops cage 101 by gripping guide rail 103.
That is, when excessive speed of the elevator is detected by speed governor 105 provided in the mechanism chamber, a rope clamping element 106 incorporated in a speed governor 105 is actuated, causing speed governor rope 107 that passes over the sheave of speed governor 105 to be gripped. When speed governor rope 107 is gripped, emergency stop device 104 is actuated by means of a safety link 108 mounted on cage 101.
FIG. 2 shows a typical speed governor employed in a high-speed elevator. This speed governor is a type of centrifugal speed governor. When sheave 108 mounted on speed governor rope 107 is rotated, this rotation is transmitted by means of a rotary shaft 113 directed in the vertical direction, by means of gear wheel 112. First links 110A constituting part of speed governor linkage mechanism 110 are mounted on a rotary shaft 113 and rotary weights (flyweights) 109 are mounted at the tips of the link arms of first links 110A. When sheave 108 is rotated, the link arms on which rotary weights 109 are mounted are opened by centrifugal force C acting on rotary weights 109, thereby raising or lowering a shaft sliding sleeve mounted on rotary shaft 113. A support shaft of a second link 110B constituting another part of speed governor linkage mechanism 110 is mounted on the shaft sliding sleeve. Second link 110B is moved with displacement of the shaft sliding sleeve in the vertical direction and when the amount of displacement of the shaft sliding sleeve exceeds a prescribed value, a hook (not clearly shown in the drawing) provided at the end of the second link 110B is released from rope clamping element 106. Rope clamping element 106 thereby grips speed governor rope 107, causing the movement of speed governor rope 107 to be arrested. When this happens, emergency stop device 104 is actuated by means of a safety link 108 mounted on cage 101 (see FIG. 1).
However, typically, in order to achieve stable operation and to prevent unwanted operation, the speed governor is adjusted such that the first and second links 110A and 110B i.e. speed governor linkage mechanism 110 are not operated until the rated operating speed of the elevator cage has been slightly exceeded. With this object, a speed adjustment spring 111 is provided on first link 110A; this speed adjustment spring ill generates a balancing force opposing centrifugal force C that acts on the rotary weights 109 at the rated speed of travel of elevator cage 101. Also, speed adjustment spring 111 is adjusted so as to generate a spring force such as to restrict the movement of speed governor linkage mechanism 110 such that second link 100B actuates rope clamping element 106 just when the speed of cage 101 exceeds the rated value.
The speed governor shown in FIG. 2 is called an xe2x80x9cupright typexe2x80x9d speed governor, since the rotary shaft 113 of rotary weights 109 is directed vertically upwards. In contrast, there are also available xe2x80x9chorizontal typexe2x80x9d centrifugal speed governors, in which the rotary shaft of the rotary weights is directed horizontally. An example of such is shown in FIG. 3. The construction of the speed governor shown in FIG. 3 can be understood by reference to the construction of the speed governor shown in FIG. 5, which is described in detail later, in the section xe2x80x9cDetailed description of the preferred embodimentsxe2x80x9d. The speed governor shown in FIG. 3 is described with the object of a comparative explanation of the technical effect with the speed governor according to the present invention in the section xe2x80x9cDetailed description of the preferred embodimentsxe2x80x9d later; it is not the case that the entire construction of the speed governor shown in FIG. 3 is publicly known.
In the upright type centrifugal speed governor shown in FIG. 2, in order to convert the rotation of sheave 108 about a horizontal axis into rotation about a vertical axis it is necessary to provide a gear wheel 112. This has the drawback that the mechanism becomes complicated and the number of components are increased. On the other hand, since the mass of rotary weights 109 and/or link mechanism 110A acts as a balancing force opposing the centrifugal force C acting on centrifugal weights 109, there is the advantage that operation of the speed governor can be restrained by these masses.
In contrast, in the case of the horizontal type of centrifugal speed governor shown in FIG. 3, since the rotary shaft of rotary weights 19 and the rotary shaft of the sheave can be shared, a mechanism such as a gear wheel is unnecessary. The number of components can therefore be decreased compared with the upright type. Also, since the rotary shaft of sheave 11 rotates the rotary weights directly, there is the advantage that the speed governor operates linearly in respect of changes of speed of movement of the elevator i.e. the advantage that precision of the speed governor is increased. However, since the pair of rotary weights 19 and the links 16 associated therewith are arranged in a condition with their weights balanced about rotary shaft 13, the mass of rotary weights 19 and/or link 16 and the like does not act as a balancing force opposing centrifugal force C. There is therefore the disadvantage that movement of the speed governor linkage mechanism must be restrained i.e. controlled solely by means of the spring force generated by speed adjustment spring 26.
The magnitude of the centrifugal force C acting on the rotary weights is expressed in the form:
C=mrxcfx892=mv2/r 
where C is the centrifugal force, m is the mass of the rotary weights, r is the radius of rotation of the rotary weights, xcfx89 is the angular velocity of the rotary weights and v is the elevator speed.
As can be seen from this equation (expression), the centrifugal force C is proportional to the square of the rotational speed. In recent years, very high-speed elevators of rated speed surpassing 600 m/min have appeared. In the speed governors of such high-speed elevators, as shown in FIG. 4, not only the magnitude of the centrifugal force C itself acting on the rotary weights but also the range of the centrifugal force C (i.e. the difference of the centrifugal force at the rated speed and the centrifugal force under excess speed conditions under which the emergency stop device would be expected to be actuated) is much greater than in a conventional elevator. Consequently, a speed governor is required having a function of being able to control in a reliable fashion actuation of the speed governor linkage mechanism and rotary weights, over a wide range of speeds.
That is, as the rated operating speed of the elevator becomes higher, the centrifugal force in the narrow range of speeds between commencement of operation of the speed governor linkage mechanism and actuation of the emergency stop device increases abruptly. In order to obtain stable performance, the spring constant of the speed adjustment spring must therefore be made small so that the change of controlling force for opposing the centrifugal force is made gradual.
On the other hand, since the speed of commencement of operation of the speed governor linkage mechanism is also high, the centrifugal force C when operation of the speed governor linkage mechanism commences also becomes high and the balancing force needed to restrain operation of the speed governor linkage mechanism also becomes large. Consequently, in a centrifugal speed governor of the horizontal type in which the mass of the rotary weights and/or speed governor linkage mechanism and the like does not act in opposition to the centrifugal force C, a speed adjustment spring capable of generating a large force is necessary.
Consequently, in a horizontal type centrifugal speed governor, a speed adjustment spring is needed that has a small spring constant and that is capable of generating a large balancing force. This means that a speed adjustment spring of extremely large external dimensions becomes necessary. This makes it impossible to construct a speed governor in a restricted space. Also, even if such a governor could be constructed, since the spring constant of the speed adjustment spring is small, the effects of manufacturing errors of the speed adjustment spring and/or individual differences of the speed governors would be considerable, making it impossible to provide a speed governor of stable performance.
Accordingly, one object of the present invention is to provide a novel speed governor of the horizontal type of excellent ease of manufacture and maintainability and high reliability, wherein the speed adjustment spring and speed governor main body can be made of small size and an elevator employing the speed governor.
In order to achieve this object, the present invention is constituted as follows. Specifically, according to the invention there is provided an elevator speed governor comprising:
a rope clamping element capable of gripping a speed governor rope for actuating an emergency stop device provided on the cage of an elevator;
a sheave that rotates with a speed corresponding to the speed of the cage, being engaged by the speed governor rope;
a rotary weight that rotates about an axis of rotation directed horizontally, being linked with rotation of the sheave and that is displaced by centrifugal force so as to move away from the axis of rotation;
a speed governor linkage mechanism on which the rotary weight is mounted and that is moved with displacement of the rotary weight and that actuates the rope clamping element if its movement exceeds a prescribed range;
a speed adjustment mechanism provided in the speed governor linkage mechanism that is displaced with movement of the speed governor linkage mechanism and that generates a first balancing force that restrains movement of the speed governor linkage mechanism by resilient force generated in accordance with the amount of this displacement; and
a balancing weight provided in the speed governor linkage mechanism and that loads the speed governor linkage with a second balancing force produced by weight acting on this balancing weight that restrains movement of the speed governor linkage mechanism.